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Chicago Telephone Supply CTS Speakers

Wigwam Jones

Wigwam Jones

Caesar non supra grammati
I know that CTS supplied many of the speaker drivers for many loudspeaker manufacturers in the earlier days of 'hi-fi' audio. I see them all the time when I open up an old speaker. Often they still work; and often they have relatively small alnico magnets, cloth or rubberized surrounds, and stamped steel baskets. However, I also realize that doesn't necessarily make them bad!

I found out that the company is still around after all these years:

http://www.ctscorp.com/about/beginnings.htm

But my real question - is there anything particularly good or bad about these old speaker drivers? Would one necessarily replace a working CTS driver just because it was a CTS driver, or is it generally acceptable if it's in working condition? They sure do sell for low prices here and there; a sleeper or appropriately priced for what they are? Would you ever build a speaker based on vintage CTS drivers the way some people do with EV or Utah drivers? What about their full-range speaker drivers (yes, I'm familiar with the various full-range discussion forums and websites)?

Interested in any comments pro or con about CTS speaker drivers.
 
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CTS was a good, middle-of-the-road speaker driver manufacturer. I'd put them squarely on a par with stuff like Eminence, Credence, Utah and the like. Some of their stuff was as good as or better than Jensen, some of it was cheaper-made, more like Utah or Oxford. They built a LOT of different stuff for a lot of DIFFERENT clients, to varying degrees of precision and accuracy. But, for their stated applications, they've always seemed to work well...

Regards,
Gordon.
 
Would one necessarily replace a working CTS driver just because it was a CTS driver, or is it generally acceptable if it's in working condition?
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I can't really give a blanket answer, but based on my experience some of the OEM CTS woofers such as those used in Altec speakers were made to the speaker designer's specs. They were well designed, and well built making them difficult to improve on in terms of cost and practicality.

Sadly, that cannot be said for some of the paper cone tweeters of the same origin and vintage, they were just mediocre at best. The phenolic ring tweeters however were, and are to this day very good.

Would you ever build a speaker based on vintage CTS drivers the way some people do with EV or Utah drivers?
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There's no good reason not to, especially if you have sourced some of their better driver examples.

Important to note that there were many design similarities among the base model drivers from CTS, Jensen, Utah, and Eminence. I'm not at all an expert with the company histories and will defer to others for particulars, but there were some working as well as inherited relationships among those companies and important design/engineer individuals that moved about working for them.
 
Thanks, guys! Question - if buying raw vintage drivers and you don't know what they came out of, how would one choose some of the 'better' examples instead of some of the 'not so good' examples? Is there a way of telling by looking at them, or does one kind of have to measure and/or listen to them to find out which is which?
 
Wigwam Jones said:
Thanks, guys! Question - if buying raw vintage drivers and you don't know what they came out of, how would one choose some of the 'better' examples instead of some of the 'not so good' examples? Is there a way of telling by looking at them, or does one kind of have to measure and/or listen to them to find out which is which?
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I don't think you can ever go wrong with attempting to find the drivers with the biggest magnet assemblies. Certainly not the only criteria, though.
 
Phototone said:
I don't think you can ever go wrong with attempting to find the drivers with the biggest magnet assemblies. Certainly not the only criteria, though.
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Thanks! Funny thing, I was considering asking just exactly that, but I didn't want to seem stupid! Hey guys, should I look for the ones with the biggest magnets or what, hur, hur, hur? I guess my first instinct was right after all?

:banana:
 
Most CTS cone material looks the same to me, despite the color. As long as there is some heft to the magnet structure, they should work well.
 
Phototone said:
I don't think you can ever go wrong with attempting to find the drivers with the biggest magnet assemblies. Certainly not the only criteria, though.
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That is not necessarily true. A large magnet assembly, in general, will increase the efficiency but it will lower the Qts (BL^2) and will overdamp the driver decreasing the low frequency response, Fs.
 
They made a really nice 4" midrange/extended range/fullrange driver (including, to OEM spec, the early Bose 901 drivers) used in many, many commercial designs.

I have a pretty limited repertoire of stories (as you all unfortunately already knew!): one of mine is the lowly HH Scott S-15 three-way. Perhaps one of the most indistinguished sealed box "monkey coffin" speakers you'll ever see; populated by three almost generic looking CTS drivers - but they're quite fine sounding little loudspeakers. Quite fine, indeed.

scotts-15drivers.jpg
 
bowtie427ss said:
I think the Klipsch K-33 woofer was CTS, until it became a later revision which i think was essentially the same woofer except built by Eminence.
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K33B was CTS. Used from the late 60s to the mid 70s in Cornwalls, LaScalas and such.

K33E was the Eminence- built successor. Used after the mid 70s in the same speakers.

They are very much alike, in parameters and performance. I personally believe that you could install one of them in one speaker cabinet in a pair, and the other kind in the other cabinet in the pair, and probably not hear an audible difference whatsoever.

BTW: The original K33 was, IIRC, Jensen or Rola/Jensen. Used up to the late '60s (there seemed to be some overlap, where Klipsch was using K33 and K33B drivers at the same time, around 1968 or so)...

Regards,
Gordon.
 
I have a pair of CTS 6 inch woofers along with EPI tweeters in SOUND DYNAMICS cabinets that sound better than most modern speakers. These woofers were made in the 1970's with rubber surrounds that have remained compliant for over 30 years.
 
I agree as well- the CTS line was pretty good. As I recall their cone mids were some of the better ones of the day rivaling Phillips. Another company of that era I like as well was the Beck line of drivers. A few of thier 12" woofers were some of my favorite!
DC
 
Wigwam Jones said:
Thanks! Funny thing, I was considering asking just exactly that, but I didn't want to seem stupid! Hey guys, should I look for the ones with the biggest magnets or what, hur, hur, hur? I guess my first instinct was right after all?

:banana:
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Not necessarily. I have two systems that use CTS 10" woofers.

Those in the Avid 102's have a rather large and heavy ceramic magnet, and rubber surrounds.

Those in the ADC 303ax's have a puny looking alnico magnet and doped cloth surrounds. Outwardly they look very similar to those in Mr. H's Scotts, except the ADC's have inverted surrounds.

But in their respective 2-cubic foot (acoustic suspension) boxes, they both work darn well, with good extension in the bottom end, an absence of the dreaded mid-bass hump, and better midrange than people generally expect from 10" two-ways.

I'd give the Avids a slight edge in detail and dynamics on the lowest notes, but really they're both darn good reproducers.

Almost forgot to add this, I think CTS made some woofers with pleated paper surrounds, and small voice coils. Speaking without experience, I'd guess those would be the ones to avoid, at least for hi-fi.
 
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googling "Mcgee radio catalog" will render some interesting pages showing many different CTS drivers, back in the day Mcgee sold tons of them, some as pre-assembled systems already mounted on a baffle just needing a DIY box.
 
My old AVID 100 speakers used an all-CTS line up.
8" CTS Alnico magnet woofers with rubber surrounds, and a pair of CTS phenolic ring tweeters.
Consumer Reports gave these speakers a "Best Buy" rating in 1974.

Steve
 
The Gale CS-401 series which has a bit of a cult following uses the CTS woofers. I was quite surprised to see such an unimpressive looking driver in such a well regarded speaker but I guess they sound better than they look.
 
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